The jokes shown employ the comical device of contrast, which is morality-neutral. From this standpoint, the study did not test affinity for dark humor but for other aspects of humor. By the way, a response to jokes like this is mediated by the lower, more primitive parts of our brain.
The report potentially leads to the false conclusion that preference for dark humor is intelligent, and plenty of readers will, after seeing this, foolishly seek dark humor and dark topics in general.
The analysis of any aspect of morality has nothing to do with humor. It employs the highest areas of our brain and mind, and anyone laughing at “dark jokes” are just as likely to hold the same traditional moral values which contradict the jokes.
Dark to light is the direction our world is taking, not light to dark.
I would highly question the mental performance of anyone who celebrates darkness, starting with Brandon Specktor and his handlers.